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Source https://es.wikipedia.org/wiki/Quimioterapia
Chemotherapy

Definition of Chemotherapy

Chemotherapy is a therapeutic technique that consists of the administration of chemical substances for treatment. It is currently one of the most widely used therapeutic methods in the treatment of cancer, using a wide variety of antineoplastic drugs     

Historical review

Main article: History of chemotherapy The term chemotherapy refers generally to the treatment of cancer, although its historical significance is broader. In a simpler sense, chemotherapy refers to the treatment of an ailment through the use of chemical substances. As such, the term has been used for non-oncological use, such as the use of antibiotics (antibacterial chemotherapy). In that sense, the first modern chemotherapeutic agent was arsphenamine, an arsenic compound discovered in 1909 and used to treat syphilis. Later sulphamides and penicillin followed. Other uses that have been termed chemotherapy are the treatment of autoimmune diseases such as multiple sclerosis, dermatomyositis, polymyositis, lupus, rheumatoid arthritis and suppression of transplant rejection (see Immunosuppression).

Cancer-specific chemotherapy began in the 1940s, with the first uses of mustard gas and folic acid-antagonistic drugs as antineoplastic agents. The development of anti-cancer drugs has now become a multimillion-dollar industry.     

Cancer chemotherapy

The drugs used in antineoplastic chemotherapy are called cytostatic or cytotoxic drugs.

Mechanism of action



The essential aim of chemotherapy is to destroy the tumor cells, in order to achieve the disappearance, arrest or reduction of the disease. The drugs used in this type of treatment are called antineoplastic or chemotherapeutic.

The process of dividing healthy cells is strictly regulated by control mechanisms, which tell the cell when to divide. Malignant tumors are characterized on the contrary, since they are formed by altered cells capable of multiplying uncontrollably and even of invading and affecting adjacent or distant organs, which is called metastasis. Thus, chemotherapy acts in the division phase of the tumor cell, preventing its multiplication and eventually destroying them. Over time, if chemotherapy works, a decrease or disappearance of the malignant tumor will be achieved.

Anti-cancer drugs reach virtually all tissues in the body, without differentiating malignant cells from healthy cells. This causes in the patient a series of side effects, which usually disappear after the end of treatment. Healthy cells that are most often damaged involve bone marrow, digestive tract and hair follicle cells, resulting in the most common side effects of chemotherapy: immunosuppression, asthenia, mucositis and alopecia, among others. Such effects are usually transient, although if they do not become controlled or tolerated by the patient they can produce toxicity and temporarily suspend the chemotherapy treatment.

Therefore, in an attempt to mitigate the side effects, in the last years have been designed anticancer drugs that act directly against the abnormal proteins of the cancer cells, what is denominated directed therapy     

Types of Chemotherapy

Chemotherapy is not usually the only treatment of cancer, since it is usually combined with surgery and radiotherapy, a modality called combined or multidisciplinary treatment.

Depending on the purpose and pharmacological combination, the following types of chemotherapy are distinguished:

Curative: Your goal is to cure the disease, when it is in a suitable stage.

Palliative: Its intention is to control the symptoms produced by the tumor, which is already at an advanced stage and inoperable. Therefore, it seeks to improve as much as possible the quality of life of the patient as well as increase their survival.

Adjuvant: is usually given following a main treatment such as surgery, to decrease the incidence of metastasis.

Neoadjuvant or induction: begins before any surgical treatment or radiotherapy, in order to evaluate the effectiveness of the treatment. It decreases the tumor stage, being able to improve the results of the surgery and of the radiotherapy and, in some occasions, the answer obtained when arriving at the surgery is a prognostic factor.

Mono chemotherapy: administration of a single antitumor drug. It consists of a judicious rotation of the available drugs (sequential monochemotherapy), in cycles in which a single compound is administered until control of the pathology or until clinical evidence of its inefficacy is demonstrated. With monochimotherapy, the neoplasias that respond best (leukemias and lymphomas) hardly exceed 30% of remission, whereas in solid tumors, treated with even more effective drugs and under the most favorable conditions, there is no adequate response beyond 10- fifteen %. For this reason, the application of sequential monochemotherapy is nowadays restricted in the treatment of neoplasias.

Polychemotherapy: combination of several cytotoxic agents that act with different mechanisms of action, synergistically, in order to decrease the dose of each individual drug and increase the therapeutic potency of all substances together. It is usually defined by the type of drugs that make up the association, dose and time in which it is given, forming a chemotherapy regimen.

Concomitant radiochemotherapy: is administered concurrently or simultaneously with radiation therapy, in order to enhance the effect of radiation or to act spatially with it, ie to enhance the local effect of radiation and To act systemically with chemotherapy.

In both monkey and polychemotherapy, and according to both the management guidelines and the patient's clinical conditions, medications for the management of secondary symptoms, such as ondansetron (concomitant with the antineoplastics), can be administered concomitantly with the antineoplastic agents ( Antiemetic), amifostine (nephroprotection), dexrazoxane (cardioprotection), mesna (used to reduce bladder irritation), or dexamethasone.     

Side Effects

Chemotherapy treatment can spoil cancer patients, as they also destroy normal cells, especially those that divide more quickly. These effects, although usually transient, can become chronic, which can extremely debilitate the patient, especially if administered for long and continuous periods of time. In some cases, when the side effects are very intense, toxicity occurs, which can lead to the temporary cessation of antineoplastic treatment. Side effects depend on the chemotherapeutic agent and the most important are:

1) Alopecia: is the most visible side effect, due to the change of body image, and which most affects psychologically the sick. However, hair loss depends on the amount and type of drug, not occurring in all cases. In addition, between four and six weeks after the end of treatment, hair regrows.

2) Nausea and vomiting: They may be relieved with antiemetics such as metoclopramide or with serotonin type 3 receptor antagonists such as dolasetron, granisetron and ondansetron. 3) Diarrhea or constipation:

4) Anemia: due to the destruction of the bone marrow, which decreases the number of red blood cells. Sometimes, blood transfusion or erythropoietin administration is needed to mitigate anemia.

5) Immunodepression: Virtually all chemotherapy regimens can cause a decrease in the effectiveness of the immune system, such as neutropenia that can lead to infection, sepsis and death if not detected and treated on time. Neutropenia can be resolved with granulocyte-colony stimulating factor (G-CSF) administration such as filgrastim.

6) Hemorrhage: due to the decrease in platelets due to bone marrow destruction.

7) Cardiotoxicity: Chemotherapy increases the risk of cardiovascular disease (eg adriamycin).

8) Hepatotoxicity: mainly affects the liver and its functions.

9) Nephrotoxicity: mainly affects the kidneys and their functions.

10) Tumor lysis syndrome: occurs with the destruction by chemotherapy of malignant cells from large tumors such as lymphomas. This serious and fatal side effect is prevented at the beginning of treatment with various therapeutic measures. 11) Decreased clotting factors: When the body is in a state of emergency and weakened, several processes, including coagulation factors, are atrophied and if we add the decrease in platelets, the patient Will have difficulty forming thrombi.

12) Sterility: Some chemotherapeutic drugs destroy cells that produce sex hormones and gametes, disabling the person to procreate.

13) Asthenia

14) Cognitive disorder
    
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